Why does OmniGraffle have a page resolution of 567 pixels. Is there any way to change that? It's way too low. I've tried changing the scale in OmniGraffle Professional and it doesn't seem to have any effect on the size of an image that can fit on a page.

I'm working with bitmap images because I'm doing iPhone screen layouts. So the fact that much of OmniGraffle is vector-based and resolution independent is irrelevant. I need to be keeping track of pixels.